Influence of large-scale atmospheric circulation on climate variability in the Greater Alpine Region of Europe

The climatic variability in the Greater Alpine Region (GAR) of Europe has a diverse character: it exhibits differences between winter and summer, and between its individual subregions. The large-scale atmospheric circulation, as expressed by the mean sea level pressure (MSLP) patterns in the wider Euro-Atlantic region, plays a significant role in the climate variability in winter, but less in summer. In winter, high-altitude temperatures are markedly linked with the Northern Hemisphere (NH) zonal circulation, as expressed by the NH annular mode (NAM), whereas the low-level temperature field is associated more with the circulation over the NE Atlantic. The Alpine mountain chain delimits the different winter precipitation regimes between the northern and southern side of the GAR. While a British Isles-centered pressure pattern plays the principal role in influencing northern Alpine precipitation, the North Atlantic Oscillation (NAO), and in particular its Mediterranean component, is the large-scale atmospheric mode affecting precipitation over the southern Alpine region. The impact of the El Nino/Southern Oscillation (ENSO) phenomenon on GAR climate is weak, though it is distinctly manifested within intermittent multidecadal periods. The most pronounced impact is found for late-autumn and early-winter temperature and late-winter precipitation. In these cases, GAR climate exhibits significant correlations with ENSO state of the preceding early autumn and late summer. The ENSO impact is associated with atmospheric pressure anomaly patterns in the European region indicating modifications of large-scale circulation whose effects are also found in the climates of larger areas of Europe.